what was that?

Today, during English class i fell asleep and dreamed I was in English class. then I woke up, and i was in English class, and then I woke up again. etc. etc. It happens to me every so often... I will dream myself waking up multiple times, and each layer is so realistic... Problem is, I don't remember falling asleep... meaning, i felt tired in my dream and didn't noticed anything had changed until something weird happened, and then I would wake up in another dream that was almost the same... When I finally woke up for real, i was shivering and felt extremely cold, the room was 75 F, and I was wearing a jacket. Is this normal? It happens to me often...

Chronically, no it isn't normal. Ocassionally, it's not uncommon.

The dreaming of waking up is actually a trademark of Theta sleep, which isn't so much a dream as it is an active visualization. Theta sleep is the stage when the body hasn't fully given itself over to dreaming. Your mind is nearly there, and your waking body is more or less straddling the fence. You think you're in a dream because there is juuuust enough influence from your subconscious to effect what you see, but the waking world's influence pretty much forces the visualization to mimic reality. The repeated waking up is basically when your waking mind tries to force consciousness....and fails. So you fall back onto the fence, only to have another "Hey, I'm dreaming" moment and another chance for your waking mind to force consciousness again.

weird... so, like hallucination?

No, more like your mind is trying to dream, but is VERY open to suggestion form the waking world. So any noise/smells/awareness-f-your-surroundings will affect the dream, as will any subconscious reactions to the scene you visualize.

So for instance sleeping the the classroom....
You hear the noises of the classroom - the teacher talking, classmates chatting, pencils writing, etc. So your brain simply overlaps the scene into your subconscious. Now you're "dreaming" that you're in the classroom. This is fine until you mishear (or only partially hear) what the teacher says, so your subconscious tries to translate or fill in the blanks. But the subconscious always gets it wrong, so that['s when the weird things happen. Your waking mind goes "Wait, that isn't right at all" and tries to force you to wake up. When you don't wake up, it basically starts over from the beginning of this paragraph.